A Monolithic 3D Printed Axisymmetric Co-Flow Single and Compound Emulsion Generator

We report a microfluidic droplet generator which can produce single and compound droplets using a 3D axisymmetric co-flow structure. The design considered for the fabrication of the device integrated a user-friendly and cost-effective 3D printing process. To verify the performance of the device, single and compound emulsions of deionized water and mineral oil were generated and their features such as size, generation frequency, and emulsion structures were successfully characterized. In addition, the generation of bio emulsions such as alginate and collagen aqueous droplets in mineral oil was demonstrated in this study. Overall, the monolithic 3D printed axisymmetric droplet generator could offer any user an accessible and easy-to-utilize device for the generation of single and compound emulsions

Nucleation control of quantum dot synthesis in a microfluidic continuous flow reactor

The use of microfluidics in chemical synthesis is topical due to the potential to improve reproducibility and the ability promptly interrogate a wide range of reaction parameters, the latter of which is necessary for the training of artificial intelligence (AI) algorithms. Applying microfluidic techniques to semiconductor nanocrystals, or quantum dots (QDs), is challenging due to the need for a high-temperature nucleation event followed by particle growth at lower temperatures. Such a high-temperature gradient can be realized using complex, segmented microfluidic reactor designs, which represents an engineering approach. Here, an alternative chemical approach is demonstrated using the cluster seed method of nanoparticle synthesis in a simple microfluidic reactor system. This enables quantum dot nucleation at lower temperatures due to the presence of molecular organometallic compounds (NMe4)4[Cd10Se4(SPh)16] and (NMe4)4[Zn10Se4(SPh)16]. This integration of cluster seeding with microfluidics affords a new mechanism to tailor the reaction conditions for optimizing yields and tuning product properties

Coupled Spherical-Cavities

In this work, we study theoretically and experimentally optical modes of photonic molecules—clusters of optically coupled spherical resonators. Unlike previous studies, we do not use stems to hold spheres in their positions relying, instead on optical tweezers to maintain desired structures. The modes of the coupled resonators are excited using a tapered fiber and are observed as resonances with a quality factor as high as 107. Using the fluorescent mapping technique, we observe families of coupled modes with similar spatial and spectral shapes repeating every free spectral range (a spectral separation between adjacent resonances of individual spheres). Experimental results are compared with the results of numerical simulations based on a multi-sphere Mie theory. This work opens the door for developing large arrays of coupled high-Q spherical resonators

A Monolithic 3D Printed Axisymmetric Co-Flow Single and Compound Emulsion Generator

We report a microfluidic droplet generator which can produce single and compound droplets using a 3D axisymmetric co-flow structure. The design considered for the fabrication of the device integrated a user-friendly and cost-effective 3D printing process. To verify the performance of the device, single and compound emulsions of deionized water and mineral oil were generated and their features such as size, generation frequency, and emulsion structures were successfully characterized. In addition, the generation of bio emulsions such as alginate and collagen aqueous droplets in mineral oil was demonstrated in this study. Overall, the monolithic 3D printed axisymmetric droplet generator could offer any user an accessible and easy-to-utilize device for the generation of single and compound emulsions

A Novel Monolithic 3D Printed Axisymmetric Co-flow Single and Double/Compound Emulsion Generator

Droplet microfluidics has been attracting interests of users in diverse fields of study such as cosmetics, pharmaceutical, and food industries due to its versatility in applications. This vast interest in droplet-based microfluidics is rooted in its specific capabilities to encapsulate biological and chemical reagents inside tiny amount of fluids, offering precise control over specific processes by considering efficiency of mass and heat transfer. In addition, droplets can play a significant role in an emerging field of opto-microfluidics. The softness of the droplet surfaces offers a unique structure for trapping light into a so-called Whispering Gallery Mode (WGM). In such a mode, the droplets serve as soft resonators, exhibiting unique optomechanical properties. Over the years, producing a device which is easy-to-use, cost-effective, and with sub-millimeter-droplet generation ability has always been a challenge among innovators in microfluidics. In our study, we have designed and fabricated a novel droplet generator device which can produce single droplets, and single/multiple droplets in a droplet by implementing monolithic 3D axisymmetric co-flow structure. We used a recent fabrication approach in microfluidics field, additive manufacturing, to fabricate the droplet generator. A commercial, low-cost Stereolithography 3D printer, which is able to offer acceptable transparency, small channel size, and high resolution of printing, produced this device. The device is user-friendly, and any inexpert person can conveniently utilize it. The design of the device is in a “Plug-and-Play” manner, which facilitates the connecting process of tubes to the device, overcoming a traditional issue of microfluidic devices which is fluid leakage. We took deionized water and mineral oil as popular immiscible fluids and tried different combination of generating emulsions, Water in Oil (W/O), Oil in Water (O/W), and Water in Oil in Water (W/O/W). We also investigated the impacts of change in flow rate of each immiscible fluid, which was used as inner, middle, or outer fluid, in the droplet (emulsion) generation. Also, we evaluated the size of emulsions which was influenced by flow rates and we extended our research to study possibility of generating complex droplet structures involving multiple droplets encapsulated in one outer droplet. Lastly, computational modeling of emulsification using phase field method has been performed to understand the fluid dynamics of the emulsion generation process. Overall, by using our novel 3D printed monolithic co-flow droplet generator device, generating single emulsion, monodispersed double emulsion, and multiple complex emulsions is now easier than traditional approaches and the device can be readily applicable in industry for many applications

Synthesis of a Functionalized Carbon Nanotube Graphene Composite Enabling pH-Responsive Electrochemical Sensing for Biomedical Applications

Sensing of pH value plays an important role in many fields of studies including biology, chemistry, and biomedicine. In recent years, nanomaterials have emerged as a promising sensing element for a variety of applications. In this study, we report a high-sensitivity pH sensor synthesized by a functionalized single-wall carbon nanotube graphene (FSWCNT/G) composite. This sensor was constructed with Cr/Au electrodes and FSWCNT/G sealed in a PDMS microchannel on a glass substrate. The experiments of a field-effect transistor (FET), linear sweep voltammetry (LSV), and response time measurement all proved the superiority of the fabricated composite sensor over a pristine graphene sensor. A high potentiometric gradient of 98.75 mV/pH within the operating pH range of 4-10 was obtained in direct potentiometric measurements. The composite nanosensor can be used to monitor the pH value in cancer cell solution. Moreover, the composite nanosensor was tested for cancer cell detection, and the range of the concentration detection was from 5 × 106 to 2.5 × 105 cells/mL, showing a potential way to achieve label-free cell detection

AC electroosmosis micromixing on a lab-on-a-foil electric microfluidic device

Efficient mixing of fluids in lab-on-a-chip devices is very important for many biomedical and biochemical applications. Lab-on-a-foil as a novel concept provides a method for fast prototyping or mass production of microfluidic devices based on thin and flexible films materials. In this article, electroosmosis micromixing is conducted in a lab-on-a-foil microfluidic device. With the electroosmotic flow (EOF), an efficient micromixing is realized inside a microchannel by tooth-shaped planar electrodes. The mixing performance is evaluated based on intensity measurement, and frequency sweeping is used to identify optimal performance. Furthermore, according to local intensity profiles, the EOF pattern is analyzed to provide a deep understanding on the influence of frequency and flow rate. The amplitude of voltage and the number of pairs of electrode tooth are also investigated to find the optimal conditions of the device. To the best of our knowledge, this is the first demonstration of the AC EOF in a lab-on-a-foil electric device and the exploration of EOF pattern vertically and horizontally in the microchannels. This study provides a method to optimize mixing performance in EOF-based micromixer. Furthermore, the fabrication method cast the potential for mass production of low-cost flexible electric microfluidic devices

A Monolithic 3D Printed Axisymmetric Co-Flow Single and Compound Emulsion Generator

We report a microfluidic droplet generator which can produce single and compound droplets using a 3D axisymmetric co-flow structure. The design considered for the fabrication of the device integrated a user-friendly and cost-effective 3D printing process. To verify the performance of the device, single and compound emulsions of deionized water and mineral oil were generated and their features such as size, generation frequency, and emulsion structures were successfully characterized. In addition, the generation of bio emulsions such as alginate and collagen aqueous droplets in mineral oil was demonstrated in this study. Overall, the monolithic 3D printed axisymmetric droplet generator could offer any user an accessible and easy-to-utilize device for the generation of single and compound emulsions